the value to which this cache maps the specified key,
contained within a Cache.ValueWrapper which may also hold
a cached null value. A straight null being
returned means that the cache contains no mapping for this key.

get

Return the value to which this cache maps the specified key, obtaining
that value from valueLoader if necessary. This method provides
a simple substitute for the conventional "if cached, return; otherwise
create, cache and return" pattern.

If possible, implementations should ensure that the loading operation
is synchronized so that the specified valueLoader is only called
once in case of concurrent access on the same key.

except that the action is performed atomically. While all out-of-the-box
CacheManager implementations are able to perform the put atomically,
the operation may also be implemented in two steps, e.g. with a check for
presence and a subsequent put, in a non-atomic way. Check the documentation
of the native cache implementation that you are using for more details.

Parameters:

key - the key with which the specified value is to be associated

value - the value to be associated with the specified key

Returns:

the value to which this cache maps the specified key (which may be
null itself), or also null if the cache did not contain any
mapping for that key prior to this call. Returning null is therefore
an indicator that the given value has been associated with the key.